Field of the Invention
The present invention relates to a method for processing a wafer into a thinner form.
Description of the Related Art
In recent years, in order to realize smaller and lighter devices, there has been a demand for processing wafers formed of silicon or the like into a thinner form. A wafer is, for example, thinned by grinding the back side thereof after devices such as ICs are formed in regions sectioned by predetermined division lines (streets) on the front surface thereof.
Meanwhile, when a wafer is thinned by grinding, the wafer is greatly lowered in rigidity and becomes difficult to handle in the subsequent steps. In consideration of this problem, a processing method for permitting a wafer to retain a predetermined rigidity after grinding thereof has been proposed in which the back side of a wafer is ground in correspondence to a central device region while maintaining the thickness of a peripheral portion of the wafer (see, for example, Japanese Patent Laid-open No. 2007-19461). In this processing method, the back side of a wafer is ground, for example, by use of a grinding wheel smaller than the wafer in diameter to form a recess corresponding to the device region. The rigidity of the wafer is retained by an annular reinforcement portion (annular projecting portion) remaining on the back side of the peripheral marginal region surrounding the device region. Incidentally, the annular projecting portion is removed later by such a method as cutting (see, for example, Japanese Patent Laid-open No. 2011-61137).